It will be understood that shoes are designed both in two dimensions and in three dimensions. The traditional approach was obviously using a pen and pencil, however, more recently, use of computer-aided design (CAD) packages have become the more common tool used by a shoe designer. This movement from paper to computer-based systems has occurred in a wide range of industries. Typically, there is a supplier of the basic CAD system and a multitude of companies who adapt these basic systems to the specific requirements of a particular industry. One computer-based design system available in the shoe industry is the CRISPIN system supplied by British United Shoe Machinery Limited of Leicester, England.
A typical CAD system for shoe design would include facilities for design in two dimensions, i.e. flat leather pieces and in three dimensions to see the practical effect as a perspective view of the designed shoe. The CAD system includes software to allow transformation between two dimensions and three dimensions along with facilities to simulate surface texture, decoration, colour and edge type.
An obvious requirement for the three-dimensional representation of a shoe design is a digitised map of a shoe last upon which the three-dimensional design can be superimposed. Shoe lasts traditionally have been made of wood but, more recently, lasts made of plastics materials have become common, and occasionally other materials such as steel or aluminium are used.
There are two approaches with regard to utilisation of a shoe last; the first is to design a bespoke shoe last for a particular shoe design or the alternative is to use an existing set of shoe lasts and design around them. Obviously, the first approach is more expensive and requires, after use, for the shoe lasts to either be stored in an archive or disposed of. In any event, typically, the acquisition of a CAD system will be by an existing shoe manufacturer who will wish to utilise his existing shoe lasts.
In the past, digitising a shoe last to provide a digital map of that last usable by a CAD system has been achieved by two approaches. Firstly, a laser triangulation technique has been used based upon projection of at least one laser point upon a rotating shoe last and observing the reflected pattern to determine position and/or shape. This laser triangulation technique is described in European Patent Application No. 90311179.7 (British United Shoe Machinery Limited et al). The alternative, is to use a so-called point digitiser, including a pen-like device, designed to move over the surface of the three-dimensional body in order to determine the three-dimensional body shape by variation in position of the pen-like device polled by a processor unit. In the case of shoe lasts, this roving of the point digitiser pen element over the last requires drawing a net of lines upon the last in order that all the areas of the last can be digitised by tracing with the pen these drawn lines and intersections on the last. An example of a 3-D point digitiser is MicroScribe-3D supplied by Immersion Corp. of San Jose, Calif., U.S.A.
It will be understood that drawing regularly spaced lines upon a shoe last and, then diligently following these lines with a point digitiser pen, is both cumbersome and inconvenient. Furthermore, due to the necessary manipulation of the point digitiser accurately, following the lines drawn on the shoe last may be difficult.
It is an objective of the present invention to provide a method of using a point digitiser to digitise a three-dimensional object, such as a shoe last, whilst avoiding the problems of prior line definition before digitisation.